Magneto for internal combustion engine



June 13, 1957 L. J. LECHTENBERG 2,796,453

MAGNETO FOR INTERNAL cbMEusTmN ENGINE Original Filed Nov. 8, 1954 3 Sheets-Sheet l .55 0 J Jpn/57mm";

J n 1957 L. J. LECHTENBERG 2,796,453

MAGNETO FOR INTERNAL COMBUSTION ENGINE Original Filed Nov. 8, 1954 3 Sheets-Sheet 2 .590 Jim/lumbar;

J 1957 1., J. LECHTENBERG 2,796,453

I HAGNETO FOR INTERNAL COMBUSTION ENGINE Original Filed Nov. 8, 1954 3 Sheets-Sheet 5 United States Patent MAGNETO FOR INTERNAL COMBUSTION ENGINE Leo J. Lechtenberg, Elm Grove, Wis., assignor to Briggs & Stratton Corporation, Milwaukee, Win, a corporation of Delaware Original application November 3, 1954, Serial No. 467,512. Divided and this application November 25, 1955, Serial No. 548,904

7 Claims. (Cl. 123-1465) This invention relates to internal combustion engines and refers more particularly to single cylinder, air cooled, four-stroke cycle engines of the type now widely used on power lawn mowers and many other well-known appriances.

As in the copending application of Leo J. Lechtenberg and Joseph R. Harkness, Serial No. 467,512, of which this application is a division, this invention has as its main purpose the production of an engine at less cost through simplicity of construction and reduction of assembly time. To this end the present invention has as one of its objects to provide an improved manner of mounting the elements of the magneto ignition system upon the engine.

Another object of this invention is to provide a novel breaker mechanism wherein the stationary contact is mounted on one end of the condenser to thereby obviate the need for providinga special insulated mounting for the stationary contact and at the same time enable the condenser mounting to be used for adjustment of the breaker point spacing.

In this connection it is a still further object of the invention to achieve simplicity and low cost by casting mounting means for the condenser and the breaker mechanism integrally with the crankcase casting.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is an end view of the engine of this invention viewing the same from the flywheel end of its crankshaft, parts of said view being broken away to show structural details;

Figure 2 is a side View of the engine shown in Figure l with parts thereof broken away and in section and with attention directed particularly to the component parts of the ignition system;

Figure 3 is a sectional view through the flywheel end of the crankshaft illustrating the magneto assembly of the engine, the major portion of the cover therefor being broken away;

Figure 4 is a detail sectional view through Figure 3 on the plane of the line 4-4, but to better illustrate the manner in which the breaker mechanism of the magneto is operated, this view shows the crankshaft turned 90 degrees from the position in which it is shown in Figure 3;

Figure 5 is a perspective view of the breaker arm and Patented June 18, 1957 the mounting therefor illustrating the parts disassembled; and

Figure 6 is a detail sectional view through Figure 3 on the plane of the line 6--6.

Referring to the accompanying drawings in which like numerals indicate like parts throughout the several views, the numeral 5 designates generally the crankcase-cylinder casting of the engine consisting of a crankcase portion 6 and a cylinder 7. This main casting together with a cylinder head 8 and a crankcase cover 9 comprise the entire body of the engine.

The crankshaft 10 of the engine and its camshaft (not shown) are journalled in bearings in the cover casting 9 and the end wall 11 of the crankcase-cylinder casting opposite the cover; and the flywheel 12 is mounted upon the end of the crankshaft which protrudes from the casting wall 11. The opposite, power take'oif end of the crank shaft protrudes from the cover casting. The crankshaft is of conventional construction and is drivingly connected with a piston, not shown, by the customary connecting rod, also not shown.

The cylinder head is of conventional construction with cooling fins cast integrally therewith, and has the usual spark plug 13 mounted therein. The cylinder cooling fins are cast integrally with and encircle the cylinder 7, while other cooling fins are cast integrally with a bosslike portion 14 of the crankcase cylinder casting. The intake port 15 and the exhaust port 16 are located in this boss-like portion 14 and the front face of the portion 14 is flat and has the attaching flange 17 of the carburetor and air cleaner assembly indicated generally by the numeral 18 bolted thereon.

The flywheel 12 is equipped with the customary fan blades 20 which induce a flow of cooling air into the inlet of a shroud 21 and from the outlet thereof against the adjacent, side of the cylinder. The shroud is held in position upon the engine by screws 22 threaded into bosses 23 on the casting. The inlet of the shroud is protected by the customary rotary screen 24, which is preferably mounted upon a rope starter pulley 25 suitably secured to the adjacent end of the crankshaft.

The ignition system of the engine is of the flywheel magneto type and accordingly the flywheel has a permanen't magnet 26 embedded in its rim, the pole pieces 26' of which sweep past the three legs 27, 28 and 29 of a laminated armature 30 having the customary coil 31 mounted upon its center leg 28. In the pastwhere flywheel magnetos have been used on engines, of this kind it has been customary to assemble the stator or the apparatus upon a mounting plate which in turn was mounted upon the engine. need for such plate mounting of the stator iseliminated by the fact that the stator armature is bolted directly to the side of the crankcase-cylinder casting, and to this end the casting has four supporting posts 32 extending from the side of the cylinder and into which the fastening screws 33 are screwed. The holes in the armature through which the clamping screws pass are sufficiently large :to permit the armature to be adjusted as required to give equal definite air gaps between its two outer legs and the periphery of the flywheel which provides the rotor of the magneto.

One end of the high tension secondary of the coil is, of course, connected to the center terminal of the spark plug through the customary spark plug lead 34 and one end of the primary winding is connected by a lead 35 to one of the contacts of the breaker mechanism indicated generally by the numeral 36 and which, as will be here inafter more fully described, embodies some rather novel In the present invention theand to protect the same against contact with the flywheel, a combined heat shield and guard 37 is provided. This unit forms the subject matter of the aforesaid copending application, Serial No. 467,512 and hence, has been fully illustrated and described therein. 7 i Two of the fastening screws 33 by which the stator armature is held in place also serve to mount a stamping 41 which provides a deflector within the air shroud and a mounting 42 for the governor vane (not shown). The breaker assembly 36 is mounted directly upon the casting side wall 11 and comprises a condenser 43, a breaker arm 44, a pair of normally open breaker contacts or points 45 and 46 and mechanism to effect periodic engagement thereof. One of the features of the breaker mechanism resides in the fact that one of :the breaker contacts'is mounted directly on one end of the condenser 43. This enables the insulating bushing 43 of the condenser to serve a dual function. Not only does it insulate the ungrounded condenser terminal but also the ungrounded breaker contact. In addition this construction enables the condenser mounting to provide for the adjustment of the breaker point spacing, for by sliding the condenser axially one way or the other the spacing of the breaker points is quickly and easily adjusted.

To this etfect the condenser and breaker point assembly is seated in a cradle formed by round bottomed notches 47 in a pair of parallel ribs 48'cast integral with the wall 11 at one side of a hub 49. The hub 49 is also integral with the wall 11 and forms part of the bearing for the adjacent end of the crankshaft. A strap 50 arched across the top of the condenser and drawn down tight by a clamping bolt 51 serves to hold the condenser firmly against displacement from any desired position of axial adjustment. To prevent rotation of the strap 50 about the screw 11 during the tightening thereof and during axial motion of the condenser for breaker point adjustment a projection 52 on the outer end of the strap is received between an abutment 53 and the adjacent rib 48. Endwise adjustment of the condenser, may entail slight loosening of the screw 51. This done, ascrew driver or other similar tool may be inserted between a ing 54 and the adjacent end of the condenser so that using the lug as a fulcrum the condenser may be easily slid in a direction to increase the spacing between the breaker points, and an adjacent boss 55 maybe used as a fulcrum for sliding the condenser in the opposite direction to decrease the breaker point spacing.

The lug 54 projects from a boss 56 which is radial to the hub 49 and is bored to slidably receive a breaker arm operating plunger 57. This plunger engages the underside of the breaker arm and rides upon the adjacent surface of the crankshaft to drop down onto a cam 58 in the crankshaft and thereby enable a breaker spring 59 acting on the arm 44 to momentarily close the breaker contacts once each revolution of the crankshaft, good electrical grounding of the breaker arm being assured by a flexible jumper 44 having one end thereof secured to the arm and its other end secured to the pivot post for the arm.

The manner in which the breaker arm 44 is mounted exemplifies the extent to which this invention has gone to reduce the cost of the engine and simplify its assembly. As best shown in Figure 5, the breaker arm is stamped from sheet metal and has a wide flat mounting end 60 with aligned fulcrum edges 61 which are received in a longitudinal groove 62 in apivot post 63. The post 63 to which one end of the grounding jumper 44 is secured is stepped into a socket 70 in the outer end of a boss 71 cast as an integral part of the wall 11 and a screw 72 passing through the post 63 and threaded into the boss secures the post to the boss.

Correct angular placement of the groove 62 is assured by a small key 73 integral with the boss 71 and extending in from the side of the socket 70 to enter the adjacent end of the groove 62. This locates the post 63 and holds it from turning.

The lead 35 which connects one end of the primary coil with the breaker contact 45, of course, also connects with the adjacent terminal of the condenser, and it is to be understood that the opposite terminal of the condenser is grounded as is also the movable breaker contact (via the jumper 44) and the common terminal of the primary and secondary windings.

The entire breaker mechanism is housed within a dustproof enclosure formed conjointly by a circular rim 74 on the casting wall 11 and a stamped cover 75. The cover 75 is in the form of a small inverted cup having a hole in its end wall to accommodate the crankshaft. The edge of this hole is slightly flared and engages a conical edge on the hub 49, and in like manner the peripheral edge of the cup fits a conical edge on the circular rim 74. The parts are of such relative dimensions that upon drawing the cover down in place by two screws 79 threaded into the bosses 55 extending up from the wall 11 a firm engage ment is first established between the edge of its hole and the hub and thereafter the peripheral edge of the cover is pulled down onto the beveled edge of the circular rim, it being understood that the bottom wall of the cover is sufliciently flexible or resilient to allow such sequential engagement. This achieves a dust-tight fit between the cover and the casting. I

From the foregoing description taken in connection with the accompanying drawings,'it will be readily'apparent that due to the simplicity of construction of its components, the ignition system of this invention is so easily assembled and adjusted upon the engine that the assembly time therefor is greatly reduced thus enabling a reduction in production costs of the engine.

What is claimed as my invention is:

1. A magneto assembly for internal combustion engines including a condenser having a grounded and an ungrounded terminal, a stationary ungrounded breaker contact, and a grounded movable breaker contact, characterized by a breaker arm having the movable breaker contact mounted on one end thereof; means mounting the breaker arm upon a wall of the engine; with said end of the arm which carries the movable breaker contact movable towards and from the stationary contact; a means biasing the breaker arm in its breaker closing direction; further characterized by the fact that the stationary breaker contact is mounted directly on the ungrounded terminal of the condenser so as to be insulated from ground by the same insulation which serves to insulate the ungrounded terminal of the condenser from ground; and characterized still further by the provision of means mounting the condenser for bodily sliding motion toward and from the breaker arm so that the mounting of the condenser may be used for adjustment of the breaker point setting. 7 b

2. In an internal combustion engine having a crankcase, one outer wall of which has a bearing in which the crankshaft of the engine turns: a magneto assembly for the engine including stationary and movable breaker contacts and a condenser; a breaker arm carrying the movable breaker contact; means on said wall of the engine mounting the breaker arm for rocking motion with its medial portion extending across the bearing in which the crankshaft turns; a breaker actuating plunger passing through the wall of the bearing under said breaker arm to coact with a cam surface on the crankshaft; the stationary breaker contact being mounted directly on one end of the condenser; and means mounting the condenser on said wall of the crankcase in a manner allowing endwise adjustment thereof so that the setting of the breaker contacts may be eifected by endwise bodily adjustment of the position of the condenser on said crankcase wall.

3. In an internal combustion engine having a crankcase, one wall of which carries a bearing in which the crankshaft of the engine turns, said bearing being formed partially by a hub projecting out from the crankcase wall; a magneto assembly for the engine including a condenser and a set of movable and stationary breaker contacts, the stationary breaker contact being mounted directly on one end of the condenser; a breaker arm carrying the movable breaker contact; breaker arm mounting means on said wall of the crankcase at one side of the bearing hub mounting the breaker arm for swinging movement toward and from the bearing hub; cradle means on the crankcase wall at the side of the bearing hub generally opposite the side of the bearing hub which faces said breaker arm mounting means, in which the condenser is cradled with the end thereof which carries the stationary breaker contact facing the movable contact; means for clamping the condenser down on said cradle means in a desired position of endwise adjustment; and means for moving the breaker arm on its mounting to effect opening and closing of the breaker contacts.

4. In an internal combustion engine having a crankcase, one Wall of which carries a bearing in which the crankshaft turns: a magneto assembly for the engine including a condenser and a pair of stationary and movable breaker contacts, the stationary breaker contact being mounted directly on one end of the condenser; a breaker arm carrying the movable breaker contact; fulcrum means on said wall of the crankcase having the breaker arm pivotally mounted thereon; means on said Wall of the casting defining a cradle-like seat for the condenser and holding it in a position at which the stationary contact carried thereby is properly located with respect to the fulcrum means to assure engagement of the contacts, the setting of the breaker contacts being determined by the axial position of the condenser in its cradle so that endwise adjustment of the condenser adjusts the setting of the breaker points; and means for securing the condenser in an adjusted position.

5. In an internal combustion engine, the structure set forth in claim 4 further characterized by the provision of a lug on the crankcase wall adjacent to one end of the condenser cartridge, said lug providing a fulcrum about which a lever may be rocked to slide the condenser cartridge in one axial direction.

6. In an internal combustion engine, the structure set forth in claim 4 further characterized by the fact that said fulcrum means comprises a post secured to the crankcase wall and extending perpendicularly therefrom, said post having a longitudinal groove in one side thereof and the breaker arm having a relatively long knife edge seated in said groove; and a spring acting on said breaker arm yieldingiy urging the movable contact carried thereby toward the stationary contact and holding the knife edges of the breaker arm seated in said groove.

7. In an internal combustion engine, the structure set forth in claim 6 further characterized by the fact that said crankcase wall is provided with a shallow substantially cylindrical well into which the fulcrum post is stepped; a screw passing through the fulcrum post and threaded into the wall to hold the post in place; and a key extending inwardly from the side of the well and of a size to be received in the adjacent end portion of the longitudinal groove in the post to thereby define the angular position of the post on the crankcase wall.

References Cited in the file of this patent UNITED STATES PATENTS 

